Fuel Economy Getting Worse? Common Causes Houston Drivers Should Check

Your car used to get 28 miles per gallon. Now it is getting 22. Six MPG might not sound like much, but over a year of Houston driving, that is hundreds of dollars in extra fuel. Here is what might be causing it.

Tire pressure: The simplest and most overlooked cause. Underinflated tires increase rolling resistance, and every 1 PSI below optimal costs about 0.2% in fuel efficiency. In Houston's temperature swings, tire pressure fluctuates constantly. Check and adjust monthly.

Dirty air filter: A clogged engine air filter restricts airflow, forcing the engine to work harder. Replacement costs $15-30 and takes 5 minutes on most vehicles. We check this during every service visit.

Spark plug wear: Worn spark plugs create weak combustion, wasting fuel. If your plugs are past their replacement interval, fresh plugs can noticeably improve fuel economy and power.

Oxygen sensor degradation: O2 sensors tell the engine computer how to adjust the fuel mixture. As they age, their readings become sluggish or biased, causing the engine to run slightly rich (too much fuel). Sensor replacement restores proper fuel trimming.

Fuel injector issues: Clogged injectors spray fuel in irregular patterns instead of a fine mist. This reduces combustion efficiency. On direct-injection engines, carbon deposits on the intake valves also affect efficiency.

Dragging brakes: A stuck caliper or seized slide pin keeps the brake pad partially in contact with the rotor. This creates constant friction that wastes fuel and generates heat. You may notice the wheel feeling hot after driving.

Thermostat stuck open: An engine that never reaches full operating temperature runs in "cold enrichment" mode longer, using more fuel. If your temperature gauge consistently reads below normal, the thermostat is likely stuck open.

AC compressor load: Houston drivers run the AC 10 months a year. A healthy AC system impacts fuel economy by about 3-5%. But a system with problems — an overcharged system, a dragging compressor, or excessive high-side pressure — can impact it more.

Driving habits: Aggressive acceleration, high speeds, excessive idling in drive-throughs, and short trips all reduce fuel economy. This is not a repair issue, but it is often the biggest factor.

Weight: Are you carrying unnecessary weight in the trunk? Every 100 pounds reduces fuel economy by about 1-2%.

If your fuel economy has dropped noticeably, a diagnostic can identify the mechanical cause. We check sensors, fuel trims, and mechanical systems during our mobile diagnostics across Houston.